Copy of Alloys & Metallic Bonding

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Transcript of Copy of Alloys & Metallic Bonding

Metallic bonds are formed when the valance electrons of a metal atom become delocalized or detached from the rest of the atom.AlloysHow Metallic Bonds are formed...How are atoms in a metal held together?How are metallic bonds formed?Common AlloysMain Points of Metallic BondingWhy are alloys more useful than pure metals?All metal atoms are held together through metallic bonds.

Metallic bonds can be between atoms of the same metals or between atoms of different metals.Valance electrons in metals are DELOCALIZED

(free to move around & not connected to the cation)Alloys are chemical substances where the main component is a metal.

However, the metal is mixed (not bonded!) with other elements.Brass - 67% copper, 33% zinc

Bronze - 60% copper, 39% tin, 1% aluminum & other elements

Steel - 98% iron, 1% carbon, 1% otherHas different properties then that of the pure metalCheaperDoes not rust as easilyHarder to break or damageLight weightStrongerMetal cations are held together via a

SEA OF ELECTRONS.Metals and ionic compounds both have a

crystalline structure. In a crystal the atoms are very organized,

making them

very hard (meaning not easy to break).However, metals are not as rigid as ionic compounds because the

atoms

in the sea of electrons are able to move around making metals

flexible, malleable & ductile.AlloysDelocalized electrons - free to move around between the stable cationsStable cationsSea of ElectronsProperties of Pure Metalsrust easilyvery soft (malleable)heavyexpensiveDo these sound like ideal properties for making something out of metal?Look at the list of everyday items:

JewelryCarsBuildingsBaseball batsKitchen appliancesWhile these are all made from metals, are they PURE metals?14 karat gold - NOT PURE GOLD!

92.5% Silver7.5% CopperThe Structure of Pure Metals vs. AlloysThe atoms in pure metals are very organized, which allows them to easily slide over one another when a force is appliedThe atoms in an alloy are disorganized due to the mixture of the different metals and elements. When a force is applied, the atoms are NOT able to slide over one another. This makes the alloy extremely strong.How are alloys made?Alloys can be made 2 different ways:

Melting each metal and then mixing them together.

Taking a solid piece of metal, coating it with a thin layer of the second metal (plating) and heating until they combine.